This invention relates to cutting tools, and particularly to a gear cutting rack having replaceable cutter inserts.
A common form of tool for generating involute gear teeth is a rack of spaced cutter teeth arranged side-by-side and which are brought to bear against the perimeter of a gear blank. The rack reciprocates across the face of the perimeter while the blank is indexed. The rack typically has several projecting cutter teeth that are triangular shaped and have cutting edges along the converging sides of each tooth.
A typical machine tool that uses rack type gear cutters is the Maag generating machine. When a multi-toothed cutter is used in such a machine, one of the interior teeth is subjected to the greatest loads as it generates the profile of the gear teeth that are normal to the tool. Teeth on either side of the interior cutter tooth are subjected to lower loads because they are generating only a portion of the profile on the teeth preceding and succeeding the gear teeth normal to the cutter. As a result, it is common to have uneven wear on the cutter teeth.
Heretofore, the rack gear cutters have been formed from a single block of metal. That is, the cutter teeth are machined into a single block of tool steel. These tool tacks are very expensive to manufacture. Since the cutter teeth are subjected to considerable wear, they must be resharpened and that has the effect of altering the size of the racks including the space between the cutter teeth. Unless alternative backups for each sized cutting tooth are provided, the machine tool is down while the cutter teeth are resharpened. If one of the cutter teeth should break, such as an intermediate tooth subjected to the greatest force during machining, the entire rack must be discarded and replaced.